Patent Document 1 discloses a display device that is provided with a fluorescent screen and means for scanning the fluorescent screen with blue excited light to form an image.
The fluorescent screen is provided with first phosphor regions that contain a fluorescent material that absorbs excited light to emit red fluorescent light, second phosphor regions that contain a fluorescent material that absorbs excited light to emit green fluorescent light, and non-fluorescent regions that diffuse excited light to supply blue diffused light, and these regions are arranged periodically in the in-plane direction.
In the above-described display device, excited light is irradiated from one surface (rear-surface side) of the fluorescent screen, and images are observed from the other surface (front-surface side) of the fluorescent screen.
When the spatial angular distribution (which corresponds to the view angle) of light that is emitted from each region of the first and second fluorescent regions and the non-fluorescent regions is small, the problem of view angle dependency arises, i.e., the perceived contrast ratio or color varies according to the direction (angle) of viewing a displayed image.
In the device described in Patent Document 1, a fluorescent material that absorbs excited light in the first and second fluorescent regions releases fluorescent light radially, and this released fluorescent light is diffused equally in all directions. The diffusion in all directions of this fluorescent light is referred to as isotropic diffusion. The non-fluorescent region is also configured to diffuse diffused blue light equally in all directions.
Configuring each of the first and second fluorescent regions and the non-fluorescent regions to produce isotropic diffusion enables an increase in the spatial angular distribution (view angle) of light that is emitted from these regions and enables a solution to the problem of view angle dependency.
However, when each of the first and second fluorescent regions and the non-fluorescent regions are configured to produce isotropic diffusion, diffused light in each region is exited in both the direction toward the front surface and the direction toward the rear surface. In this case, the diffused light that is exited toward the rear surface does not contribute to the formation of images and therefore decreases the light utilization efficiency.
In the device described in Patent Document 1, a reflection layer is provided on the rear surface of the fluorescent screen that transmits blue excited light and reflects light of other colors (including red and green fluorescent light).
The reflection layer is a wavelength-selective reflection layer that is made up of, for example, a dielectric multilayer film. The red and green fluorescent light that is emitted toward the rear surface from the first and second fluorescent regions is reflected in the direction toward the front surface by the reflection layer, whereby the light utilization efficiency of fluorescent light can be increased.